When exactly did the government threaten Snowden? What did they threaten him with?

Assuming that they threatened him with prison time (I believe he was already out of the country), is the government not allowed to try and convict people based on the established law of the land if those people are following their personal moral compass? Is "I felt it was the right thing to do" an absolute defense against prosecution?

I am also curious as to how the government is responsible for Snowden fleeing to Moscow. Is Snowden responsible for his own actions or not?